Heat exchanger, especially a charge-air cooler for motor vehicles

ABSTRACT

The invention relates to a heat exchanger, especially a charge-air cooler for motor vehicles, comprising flat tubes ( 9 ) with tube ends ( 9   a ), and collecting tanks ( 1 ) which are connected to tube plates ( 4 ), said tube plates ( 4 ) comprising openings ( 8 ) provided with long sides ( 8   a ) and short sides ( 8   b ) for receiving the tube ends ( 9   a ), in addition to edge strips ( 5, 6 ) and transition regions ( 12, 13 ) which are embodied in a groove-type manner and located between the short sides ( 8   b ) and the edge strips ( 5, 6 ), the tube ends ( 9   a ) being soldered in the openings ( 8 ). According to the invention, the transition regions ( 12, 13 ) comprise a reinforcing element.

The invention relates to a heat exchanger, especially a charge-aircooler for motor vehicles, according to the preamble of-patent claim 1.

Known heat exchangers for motor vehicles, such as, for example,charge-air coolers and coolant radiators, are produced from aluminum(aluminum alloys) and soldered, this applying either only to the heatexchanger block or the entire heat exchanger, including header boxes.The heat exchanger block, especially where charge-air coolers areconcerned, is constructed from a series of flat tubes, between whichcorrugated ribs are arranged. The tube ends of the flat tubes arereceived in orifices, what are known as rim holes, of the tube bottomand are soldered to the rim holes. This gives rise to a firm andleaktight tube/bottom connection. The header boxes are soldered orwelded to the tube bottoms. For the connection between header box andtube bottom, the tube bottom has a peripheral edge strip which engagesover or under the header box and thus forms a soldering surface. The rimholes in the tube bottom extend over the entire depth of the latter,that is to say from longitudinal side to longitudinal side, there beingbetween the narrow sides of the rim holes and the edge strips atransitional region which has a channel-like, for example approximatelyU-shaped design. The tube bottom thus has an approximately rectangularlydesigned, if appropriate continuous channel which is composed of twoparallel longitudinal sides and two parallel narrow sides. Thelongitudinal sides of the tube bottom are located opposite the narrowsides of the rim holes. During operation, the header boxes are loaded bythe internal pressure of the heat exchange medium, for examplecompressed charge air. This gives rise, in the transitional regionbetween the longitudinal sides of the tube bottom and the narrow sidesof the rim holes, to deformations as a result of bending stresses whichlead to stress peaks in the region of the narrow sides of the rim holes.The tube/bottom connection, in particular, is subjected to thesestresses and deformations on its narrow side and in the tube cornerregions in such a way that leaks of the heat exchanger may occur.

The object of the present invention is, in a heat exchanger of the typeinitially mentioned, to improve the tube/bottom connection and to avoidadverse stresses.

This object is achieved by means of the features of patent claim 1.According to the invention, a reinforcement is provided in thetransitional region of the tube bottom. This affords the advantage thatan inadmissible deformation or flexion of the tube bottom in thetransitional region is avoided and the harmful stress peaks are reduced.The tube bottom, which, by being produced from a sheet steel billet, hasapproximately the same wall thickness in the remaining region, thusbecomes deformable to a lesser extent on the longitudinal sides in theregion of the tube narrow sides. The tube/bottom connection isconsequently subjected to less or virtually no bending stress, butessentially to shearing stress, which constitutes an appreciably morefavorable load.

The reinforcement of the transitional region may be implemented by meansof various structural solutions which arise as advantageous refinementsfrom the subclaims. For example, the reinforcement may be configured asa material thickening, thus leading to an increased bending resistancefor the transitional region. This could take place, in production terms,by means of the compression of the material. Another advantageouspossibility for reinforcement is to reinforce the tube bottom in thetransitional region, for example, by one or more beads. Thus, bystability being increased, with the wall thickness of the tube bottomremaining the same, an increased deformation resistance would beachieved. The beads are preferably to be arranged in the region of thenarrow sides of the rim holes, in order to achieve an increased bendingresistance there.

According to a further advantageous refinement of the invention, thereinforcement is designed as a profile strip which fills thechannel-like transitional region and is soldered to the tube bottom.This profile strip likewise achieves a reinforcement, that is to say bymeans of an additional part which is connected to the tube bottom toform a bend-resistant region. Between the outer edge strip of the tubebottom and the narrow side of the rim hole, therefore, a connection,that is to say a firm bridge, is produced, which prevents a flexion ordeformation of the transitional region. The harmful bending stresses areconsequently “kept away” from the tube/bottom connection.

According to an advantageous development of the invention, the profilestrip is produced or integrated in one piece with the header box, thatis to say it forms a prolongation of the longitudinal edges of theheader box downward, that is to say in the direction of the tube bottom.This does not entail any additional outlay in terms of manufacture orassembly, since the header box is placed onto the bottom and soldered tothe latter, as hitherto.

According to a further refinement of the invention, the profile strip isdesigned as a (separate) insert strip, that is to say an additional partwhich is inserted into the channel-like transitional region and issoldered to the tube bottom. The advantage of this solution is thatmodifications do not have to be made either to the tube bottom or to theheader box. For example, such insert strips may be used for heatexchangers, especially charge-air coolers, which are to be employed forhigher charge-air pressures. Thus, by means of this simple purposefulmeasure, the same cooler can be adapted to the higher operatingstresses.

In a further advantageous refinement of the invention, the profile orinsert strips have toward the inside of the tube bottom, in the regionof the tube narrow sides, recesses which partially surround the rimholes, that is to say bear against the narrow sides and corner regionsand are supported with respect to these. Consequently, in particular,the corner regions of the tubes are also protected from harmful stresspeaks.

Exemplary embodiments of the invention are illustrated in the drawingand are described in more detail below. In the drawing:

FIG. 1 shows a detail of a charge-air cooler,

FIG. 2 shows a view of the charge-air cooler according to FIG. 1 withhatched insert strips,

FIG. 3 shows a sectional illustration of the charge-cooler according toFIG. 1 and 2,

FIG. 4 shows a view of the tube bottom with hatched insert strips,

FIG. 4 a shows a cross section through the tube bottom, and

FIG. 5 shows a further embodiment of the invention with an integratedprofile strip.

FIG. 1 shows a detail, that is to say a “slice”, of a charge-air coolerin the region of the charge-air box and of the tube/bottom connection.Charge-air coolers of this type are used for the cooling of compressedcharge air in motor vehicles, especially commercial vehicles. A headerbox 1 (also called a charge-air box) has a U-shaped design in crosssection and is preferably produced from aluminum alloy. Overall, theheader box 1 has the form of an elongate box which can be produced bydeep drawing or casting. The U-profile of the header box 1 has two legs2, 3 which form the longitudinal sides of the charge-air box. The headerbox 1 is inserted into a tube bottom 4 which has, along the longitudinalsides, edge strips 5, 6 which are angled approximately perpendicularlywith respect to a bottom plate 7. The bottom plate 7 has a multiplicityof rim holes, of which only one rim hole 8 receiving a tube end 9 a of aflat tube 9 is illustrated here. The entire heat exchanger or charge-aircooler thus has a multiplicity of flat tubes, between which are arrangedcorrugated ribs, not illustrated, which form secondary heat exchangesurfaces for ambient air. The legs 2, 3 of the box profile have, ontheir lower, that is to say open side, connecting portions 2 a, 3 awhich overlap with the edge strips 5, 6 in the tube bottom 4 and aresoldered to one another in this region. What are known as insert strips10, 11, illustrated by hatching, are arranged below the lower edges ofthe connecting portions 2 a, 3 a.

FIG. 2 shows the header box 1 according to FIG. 1 as a front view, thatis to say in a sectional plane in front of the rim hole 8. As is knownfrom the prior art, the tube bottom 4 is produced from a sheet metalbillet and therefore has essentially a constant wall thickness s; therim holes 8 are directed inward, that is to say toward the side of thebox 1. The tubes 9 project with their tube ends 9 a inward beyond therim hole 8. In a further exemplary embodiment, not shown, the rim holesare directed outward. The tubes may in this case project beyond a tubebottom surface or advantageously terminate under such a tube bottomsurface.

The bottom plate 7 is planar on the longitudinal sides of the tubebottom 4, that is to say outside the rim holes 8, but has a channel-likedesign within the edge strips 5, 6, this channel merging, on the onehand, into the bottom plate 7 and, on the other hand, into the edgestrips 5, 6, that is to say forming the transitional regions 12, 13.These transitional regions 12, 13 thus form longitudinal beads forincreasing the stability of the tube bottom 4. By the box 1 being loadedby the internal pressure caused by the compressed charge air, this givesrise in the longitudinal sides 2, 3 of the box 1 to compressive and/ortensile forces which are transmitted to the edge strips 5, 6 of thebottom and bring about bending stresses and deformations in thetransitional regions 12, 13. This is where the invention comes in withthe arrangement of the insert strips 10, 11 which are designed asprofile strips and have a profile which corresponds to that of thetransitional regions 12, 13. The insert strips 10, 11 thus bear on theoutside against the edge strips 5, 6, at the bottom against thechannel-like transitional regions 12, 13 and on the inside against thenarrow sides of the rim holes 8. Air gaps 14, 15 are left above the edgestrips 10, 11. As already mentioned, the insert strips 10, 11, whichpreferably likewise consist of an aluminum alloy, are soldered to thebottom 4, that is to say in one operation with the entire heatexchanger.

FIG. 3 shows a sectional illustration in a plane parallel to the drawingplane according to FIG. 2. In this illustration, in particular, the rimholes 8 can be seen clearly in their profile: the rim holes 8 form withthe outer wall of the tube 9 an acute angle which is filled with asolder meniscus 16 after soldering. Above the solder meniscus, the tubebears against the rim hole 8 with a relatively narrow gap. As mentioned,the rim hole 8 forms, with the two outer edge strips 5, 6 of the bottom,the transitional regions 12, 13 which here are in the form of anasymmetric U in cross section and are filled by the insert strips 10,11. Between the edge strips 5, 6 and the rim holes 8, more precisely thenarrow sides of the rim holes, the insert strips 10, 11 form a firmbridge which prevents a deformation of the transitional regions 12, 13.Consequently, the stress peaks occurring in the prior art are reduced,and the tube/bottom connection is relieved considerably in the region ofthe narrow sides. The air box 1 can thus withstand higher pressures.

FIG. 4 shows a sectional illustration along the line IV-IV, as depictedin FIG. 4 a. Correspondingly to the form of the tubes 9, not illustratedhere, the rim holes 8 have an approximately rectangular inner and outercross section with longitudinal sides 8 a and narrow sides 8 b. Theinsert strips 10, 11 fit snugly onto the narrow sides 8 b of each rimhole, that is to say they have in the region of the narrow sides 8 brecesses 10 a, 11 a in the form of the narrow sides 8 b. This snug fitof the insert strips 10, 11 results, together with the soldering, in avery good support of the bottom regions located opposite one another,that is to say a bend-resistant interconnected structure. The recesses10 a, 11 a may be produced by pressing.

FIG. 4 a shows the tube bottom 4 in cross section, with the rim holes 8which have an outer conical region 8 c and an inner cylindrical region 8d (adapted to the cross section of the flat tubes 9). The conical region8 c also serves as an introduction slope for the tube ends 9 a. The rimholes 8 are produced from the tube bottom plate 7 by hole-punch pressing(cf. FIG. 2).

FIG. 5 shows a further embodiment of the invention, in which the insertstrips described above are integrated with the air box, that is to sayare produced in one piece with the latter here. The tube bottom 4 isunchanged; the header box 17 has connecting regions 17 a, 17 b, thelower edges of which are designed as profile strips 18, 19 which fillthe channel-like transitional regions 12, 13 of the bottom 4. Inprinciple, the same effect as that described above is achieved by meansof this solution, that is to say a reinforcement of the transitionalregions 12, 13. Insofar as the box 17 is produced as a casting orinjection molding, the rounded profile strips 18, 19 may readily beproduced by means of the corresponding configuration of the mold. Inthis design of the air box 17 with the profiled lower edges 18, 19,therefore, the insertion of the insert strips described above isdispensed with, that is to say one operation is saved. Similarly, theprofile strips may also be fastened to the lower edges of the air box,for example by adhesive bonding.

Further solutions, not illustrated here, for reinforcing thetransitional regions are possible, for example reinforcement by means ofbeads, that is to say an increase in the bending resistance by anappropriate shaping for increasing the moment of resistance. The beadsmay be formed in the region of the narrow sides of the rim holes at thesame time as the production of the bottom. Furthermore, there is thepossibility of designing the transitional region with a greater wallthickness, which may be carried out, for example, by compressing thebottom in the transitional region. These solutions, too, have the resultthat the harmful stress peaks in the region of the tube/bottomconnection, that is to say in the region of the narrow sides and of thetube corner regions, are reduced.

REFERENCE NUMERALS

1 Charge-air box

-   -   2 Longitudinal side        2 a Connecting region        3 Longitudinal side        3 a Connecting region        4 Tube bottom        5 Edge strip        6 Edge strip        7 Bottom plate        8 Rim hole        8 a Longitudinal side        8 b Narrow side        8 c Conicalfliregion        8 d Cylindrical region        9 Flat tube        9 a Tube end        10 Insert strip        11 Insert strip        12 Transitional region        13 Transitional region        14 Gap        15 Gap        16 Solder meniscus        17 Header box        17 a Connecting region        17 b Connecting region        18 Integrated profile strip        19 Integrated profile strip

1. A heat exchanger, especially a charge-air cooler for motor vehicles,with flat tubes having tube ends, and with header boxes which areconnected, especially soldered, to tube bottoms, the tube bottoms havingorifices with longitudinal sides and narrow sides for receiving the tubeends, furthermore edge strips and transitional regions of channel-likedesign between the narrow sides and the edge strips, and the tube endsbeing soldered in the orifices, wherein the transitional regions have areinforcement.
 2. The heat exchanger as claimed in claim 1, wherein thereinforcement is designed as a material thickening.
 3. The heatexchanger as claimed in claim 1, wherein the reinforcement is designedas a stiffening, especially as a bead.
 4. The heat exchanger as claimedin claim 1, wherein the reinforcement is designed as a profile stripwhich at least partially fills the transitional region and which issoldered to the tube bottom.
 5. The heat exchanger as claimed in claim4, wherein the profile strips are produced in one piece with the headerbox.
 6. The heat exchanger as claimed in claim 4, wherein the profilestrips are designed as insert strips.
 7. The heat exchanger as claimedin claim 4, wherein the orifices are designed as inwardly directed rimholes, and in that the profile strips have recesses which are adapted tothe form of the narrow sides of the rim holes.
 8. The heat exchanger asclaimed in claim 1, wherein the orifices are designed as outwardlydirected rim holes.
 9. The heat exchanger as claimed in claim 5, whereinthe orifices are designed as inwardly directed rim holes, and in thatthe profile strips have recesses which are adapted to the form of thenarrow sides of the rim holes.
 10. The heat exchanger as claimed inclaim 6, wherein the orifices are designed as inwardly directed rimholes, and in that the profile strips have recesses which are adapted tothe form of the narrow sides of the rim holes.
 11. The heat exchanger asclaimed in claim 2, wherein the orifices are designed as outwardlydirected rim holes.
 12. The heat exchanger as claimed in claim 3,wherein the orifices are designed as outwardly directed rim holes. 13.The heat exchanger as claimed in claim 4, wherein the orifices aredesigned as outwardly directed rim holes.
 14. The heat exchanger asclaimed in claim 5, wherein the orifices are designed as outwardlydirected rim holes.
 15. The heat exchanger as claimed in claim 6,wherein the orifices are designed as outwardly directed rim holes. 16.The heat exchanger as claimed in claim 7, wherein the orifices aredesigned as outwardly directed rim holes.